Construction adhesives can be a major source of indoor air quality problems, often more so than the products they go with—but even green builders focused on low-emitting finishes may keep using high-emitting adhesives because they trust a product and know how it performs. The good news is that adhesive manufacturers have been developing lower-emitting products for some time, and there is a growing array of high-performing alternatives for different applications.
Many adhesives now meet stringent VOC content limits from South Coast Air Quality Management District (SCAQMD) and California Air Resources Board (CARB). However, these VOC limits are really designed for minimizing smog creation, not for protecting human health—so products formulated to meet these limits may include hazardous, but EPA “exempt” compounds, such as toluene. Adhesives certified to the California Department of Public Health (CDPH) 01350 standard are designed to be protective of occupant health. Certifications that meet or exceed this standard include SCS Indoor Advantage Gold, Greenguard Children & Schools, Carpet and Rug Institute Green Label Plus, and FloorScore.
Current methods for evaluating emissions are still an imperfect measure for wet-applied products like adhesives—it’s difficult to test for VOCs when the product is curing and letting off both water vapor and transitional curing compounds, so test procedures typically wait until initial off-gassing is complete and then test for long-term emissions that may cause chronic health concerns. That’s fine for occupants, but not so good for installers. Looking for low-VOC content products helps to cover that gap.
The good news is there are plenty of adhesives that are low-VOC content and meet more stringent VOC emissions protocols. The bad news is that doesn’t mean they’re good for you. Low-VOC status and the limited information required on a material safety data sheet (MSDS) provide little assurance that products don’t contain other hazards.
Ultimately it would be great to see products that provide full disclosure of material composition demonstrating that the product contains no chemical hazards of high concern, but, in an industry where chemical formula is a competitive advantage, that may be slow in coming. We already mentioned “exempt” VOCs like toluene that don’t contribute to smog but aren’t good for you. There are also some semi-volatile and nonvolatile hazards that are common in adhesives. Epoxies used for resilient flooring commonly contain bisphenol A compounds, and many polyurethane adhesives used for wood and resilient flooring contain polyisocyanate compounds in uncured form. Some adhesive types are generally safer than others. Polyvinyl acetate-based “white glue” and aliphatic resin-based “yellow glue” for woodworking applications are inherently nontoxic. Polyether-based adhesives, which are much more common in Europe, are 100% solid formulation (i.e., no VOCs) and don’t typically contain other hazards.
One thing no one can afford to forget is that no adhesive that fails in its proper application can be called “green.” As manufacturers of both finishes and adhesives seek out new and greener alternatives, changing composition can sometimes introduce performance challenges, so it’s always good to test and ask around to find what works. Any adhesive’s performance is dependent on quality installation and proper selection to match the surfaces to be bonded. Expecting a new adhesive type to perform with the same application technique may result in failure—but if the contractor didn’t review the instructions, it isn’t the adhesive that failed. While some adhesives are multipurpose, many are specific to a particular application and material (linoleum, for example, requires special adhesives due to its linseed oil content).
Make sure the adhesive you select is appropriate to the real composition of the substrates you’re trying to adhere. There are no foolproof tests for long-term performance, and manufacturer recommendations are key. If a manufacturer of the materials you’re aiming to adhere recommends a specific low- or zero-VOC, water-based product for use with its material, then use it; otherwise, consider a product known to minimize indoor air pollution and check to ensure the adhesive is appropriate for the substrates being adhered. It isn’t just performance with respect to the substrate that’s important; it also has to work on the job—a green adhesive isn’t so green if you waste half of it on the jobsite because it goes dry in the applicator, so finding a way to do the job with less waste is important, too.
Some applications are harder than others to find safer alternatives for, but thankfully there are fewer and fewer applications that require hazardous solvent-based adhesives. The best manufacturers are looking for safer alternatives for all applications—they are looking ahead of regulations and building rating systems and finding ways to reformulate all adhesives toward lower hazard content.